It is known from U.S. Pat. No. 3,383,436 that polyphenylenether resins are compatible in all proportions with polystyrene: the addition of polystyrene has chiefly the consequence of improving the hot processability characteristics of polyphenylenether.
It is known as well that the polyphenylenether resins are not compatible to an appreciable extent with thermoplastic resins different from polystyrene.
It is known, for example from U.S. Pat. No. 3,361,851, that polypropylene can be incorporated into polyphenylenether in amounts up to about 10% by weight. However, the addition of amounts exceeding 10% causes a phase separation with consequent lamination phenomena in the molded articles.
When polyethylene is incorporated into polyphenylenether, the melt-flow index and a few physical properties are considerably improved, but the amount of polyethylene that can be incorporated reaches at the most to about 5% by weight. Higher amounts than 5% cause lamination phenomena and an excessive brittleness.
Lastly, it is known that it is possible to incorporate amounts of polyolefin higher than those indicated herein when using, as compatibility-promoting agents, elastomeric block copolymers of type A B A', in which A and A', like or unlike each other, are blocks of vinylaromatic monomers and B is a block of a conjugated diolefin.
Also in this case, however, the amount of polyolefin that can be incorporated is rather low: the sum of the polyolefin amount and of the elastomeric copolymer amount does not exceed in fact 30% by weight.
Higher polyolefin amounts than those mentioned above lead, also in this case, to a phase separation and to consequent lamination phenomena.